1. Field of the Invention
The present invention is related to systems, devices and methods that couple to tissue such as hearing systems. Although specific reference is made to hearing aid systems, embodiments of the present invention can be used in many applications in which a signal is used to stimulate the ear.
People like to hear. Hearing allows people to listen to and understand others. Natural hearing can include spatial cues that allow a user to hear a speaker, even when background noise is present. People also like to communicate with those who are far away, such as with cellular phones.
Hearing devices can be used with communication systems to help the hearing impaired and to help people communicate with others who are far away. Hearing impaired subjects may need hearing aids to verbally communicate with those around them. Unfortunately, the prior hearing devices can provide less than ideal performance in at least some respects, such that users of prior hearing devices remain less than completely satisfied in at least some instances.
Examples of deficiencies of prior hearing devices include feedback, distorted sound quality, less than desirable sound localization, discomfort and autophony. Feedback can occur when a microphone picks up amplified sound and generates a whistling sound. Autophony includes the unusually loud hearing of a person's own self-generated sounds such as voice, breathing or other internally generated sound. Possible causes of autophony include occlusion of the ear canal, which may be caused by an object blocking the ear canal and reflecting sound vibration back toward the eardrum, such as an unvented hearing aid or a plug of earwax reflecting sound back toward the eardrum.
Although acoustic hearing aids can increase the volume of sound to a user, acoustic hearing aids provide sound quality that can be less than ideal and may not provide adequate speech recognition for the hearing impaired in at least some instances. Acoustic hearing aids can rely on sound pressure to transmit sound from a speaker within the hearing aid to the eardrum of the user. However, the sound quality can be less than ideal and the sound pressure can cause feedback to a microphone placed near the ear canal opening Although placement of an acoustic hearing aid along the bony portion of the ear canal may decrease autophony and feedback, the fitting of such deep canal acoustic devices can be less than ideal such that many people are not able to use the devices. In at least some instances sound leakage around the device may result in feedback. The ear canal may comprise a complex anatomy and the prior deep canal acoustic devices may be less than ideally suited for the ear canals of at least some patients. Also, the amount of time a hearing device can remain inserted in the bony portion of the ear canal can be less than ideal, and in at least some instances skin of the ear canal may adhere to the hearing device such that removal and comfort may be less than ideal.
Although it has been proposed to couple a transducer to the eardrum to stimulate the eardrum with direct mechanical coupling, the clinical implementation of the prior direct mechanical coupling devices has been less than ideal in at least some instances. Coupling the transducer to the eardrum can provide amplified sound with decreased feedback, such that in at least some instances a microphone can be placed in or near the ear canal to provide hearing with spatial information cues. However, the eardrum is a delicate tissue structure, and in at least some instances the placement and coupling of the direct mechanical coupling devices can be less than ideal. For example, in many patients the deepest portion of the ear canal comprises the anterior sulcus, and a device extending to the anterior sulcus can be difficult for a clinician to view in at least some instances. Further, at least some prior direct coupling devices have inhibited viewing of the eardrum and the portion of the device near the eardrum, which may result in less than ideal placement and coupling of the transducer to the eardrum. Also, direct coupling may result in autophony in at least some instances. The eardrum can move substantially in response to atmospheric pressure changes, for example about one millimeter, and at least some of the prior direct coupling devices may not be well suited to accommodate significant movement of the eardrum in at least some instances. Also, the naturally occurring movement of the user such as chewing and eardrum movement may decouple at least some of the prior hearing devices. Although prior devices have been provided with a support to couple a magnet to the eardrum, the success of such coupling devices can vary among patients and the results can be less than ideal in at least some instances.
Although the above described prior systems can help people hear better, many people continue to have less than ideal hearing with such devices and it would be beneficial to provide improved coupling of the transducer assembly to the eardrum and ear canal. Also, it would be helpful to provide improved coupling in simplified manner such that the assemblies can be manufactured reliably for many users such that many people can enjoy the benefits of better hearing.
For the above reasons, it would be desirable to provide hearing systems and improved manufacturing which at least decrease, or even avoid, at least some of the above mentioned limitations of the prior hearing devices. For example, there is a need to provide improved manufacturing of reliable, comfortable hearing devices which provide hearing with natural sound qualities, for example with spatial information cues, and which decrease autophony, distortion and feedback.
2. Description of the Background Art
Patents and publications that may be relevant to the present application include: U.S. Pat. Nos. 3,585,416; 3,764,748; 3,882,285; 5,142,186; 5,554,096; 5,624,376; 5,795,287; 5,800,336; 5,825,122; 5,857,958; 5,859,916; 5,888,187; 5,897,486; 5,913,815; 5,949,895; 6,005,955; 6,068,590; 6,093,144; 6,139,488; 6,174,278; 6,190,305; 6,208,445; 6,217,508; 6,222,302; 6,241,767; 6,422,991; 6,475,134; 6,519,376; 6,620,110; 6,626,822; 6,676,592; 6,728,024; 6,735,318; 6,900,926; 6,920,340; 7,072,475; 7,095,981; 7,239,069; 7,289,639; D512,979; 2002/0086715; 2003/0142841; 2004/0234092; 2005/0020873; 2006/0107744; 2006/0233398; 2006/075175; 2007/0083078; 2007/0191673; 2008/0021518; 2008/0107292; commonly owned U.S. Pat. Nos. 5,259,032; 5,276,910; 5,425,104; 5,804,109; 6,084,975; 6,554,761; 6,629,922; U.S. Publication Nos. 2006/0023908; 2006/0189841; 2006/0251278; and 2007/0100197. Non-U.S. patents and publications that may be relevant include EP1845919 PCT Publication Nos. WO 03/063542; WO 2006/075175; U.S. Publication Nos. Journal publications that may be relevant include: Ayatollahi et al., “Design and Modeling of Micromachines Condenser MEMS Loudspeaker using Permanent Magnet Neodymium-Iron-Boron (Nd—Fe—B)”, ISCE, Kuala Lampur, 2006; Birch et al, “Microengineered Systems for the Hearing Impaired”, IEE, London, 1996; Cheng et al., “A silicon microspeaker for hearing instruments”, J. Micromech. Microeng., 14(2004) 859-866; Yi et al., “Piezoelectric microspeaker with compressive nitride diaphragm”, IEEE, 2006, and Zhigang Wang et al., “Preliminary Assessment of Remote Photoelectric Excitation of an Actuator for a Hearing Implant”, IEEE Engineering in Medicine and Biology 27th Annual Conference, Shanghai, China, Sep. 1-4, 2005. Other publications of interest include: Gennum GA3280 Preliminary Data Sheet, “Voyager TD™. Open Platform DSP System for Ultra Low Power Audio Processing” and National Semiconductor LM4673 Data Sheet, “LM4673 Filterless, 2.65 W, Mono, Class D audio Power Amplifier”; Puria, S. and Steele, C Tympanic-membrane and malleus-incus-complex co-adaptations for high-frequency hearing in mammals. Hear Res 2010 263(1-2):183-90; O'Connor, K. and Puria, S. “Middle ear cavity and ear canal pressure-driven stapes velocity responses in human cadaveric temporal bones” J. Acoust. Soc. Am. 120(3) 1517-1528.